Slot machines are popular gaming machines in casinos. There are many types of slot machines and some of the slot machines have a display for displaying a plurality of cells or columns in which symbols (or indicia) are shown randomly in each game. When the symbols shown in the cells or columns form one or more winning combinations, a corresponding prize is paid to the player. Also, recent slot machines typically have a primary game and a secondary game. The secondary game may comprise any type of game, either similar to or completely different from the primary game. The secondary game is initiated upon the occurrence of a selected event or outcome of the primary game. For example, the secondary game may be embodied as a free spin game, which comprises one or a series of slot games conducted “for free”, i.e., without requiring wager or credit paid by the player. Each slot game, which contains start and stop of rotation of the reels along which symbols are arranged, may be called a reel spin. Often times, the secondary game is carried out as a bonus game of the primary game, and therefore designed so that higher prizes may be paid to the player to whereby enhance the excitement of the player.
One example of the above gaming machine is disclosed in U.S. Pat. No. 6,805,632. This patent is related to a video slot machine. The video slot machine includes a display device for displaying a plurality of symbols in a grid having a plurality of cells defined by rows and columns, a memory device for storing a pay-table, and a game controller coupled to the display device and the memory device. The game controller is adapted to randomly select the symbols to be displayed in the display device and to determine an outcome based on the displayed symbols, pay-table, and predetermined pay lines in the primary game and the secondary game. The selected symbols occasionally include a bonus symbol. The game controller is adapted to identify the presence of the bonus symbol in one of the cells of a column and to modify all of the symbols within the column to wild.
However, as the players get used to the gaming machines having primary and secondary games, the excitement provided by the gaming machines tends to be insufficient to fully satisfy the players. Thus, new features are necessary to satisfy demands of the players for greater excitement and thereby entice a longer play period. Particularly, when the secondary game is of the same type of game as the primary game (for example, when the primary game is a slot game and the secondary game consists of a free spin game), the secondary game can be less entertaining to the players. Thus, a secondary game having novel features is demanded in order to provide a higher excitement to the players. However, designing a totally new game for the secondary game would require a considerable time and cost. Under such circumstances, there is a need for a novel gaming machine having a primary game and a secondary game that can provide a higher level of excitement to the player with minimum modifications to the existing gaming machines. The gaming machine of the present invention is directed to satisfying these needs.